Kryptonite
by LuckyLadybug
Summary: Why was Zack absent when Cloud's friends were lifting him to face Bahamut SIN? Perhaps he had gone to try to talk sense into another friend, the one responsible for all the madness....


**Final Fantasy VII**

**Kryptonite**

**By LuckyLadybug**

**Notes: The characters are not mine and the story is! It was inspired when I was watching **_**Advent Children**_** one day and suddenly wondered why Zack was not present when Cloud fought Bahamut SIN and everyone was lifting him up. So here's the explanation I like to imagine. Parts of this were also inspired by Manders1953's idea of what was happening during the fight between Cloud and Sephiroth. And the prompt **_**Platonic love**_** at 30 Friends assisted, too. Some of this, especially the set-up at the beginning, is meant to explain better what was not explained in **_**Loneliness of a God**_**--which, by the way, doesn't connect with this fic, as readers will see. And the mention of Zack going to see Sephiroth before the final battle two years ago is based on an idea and an angsty ficlit of Lisa's. Thanks to everyone who gave plot help!**

* * *

The Lifestream was the unifying force on Gaia. It both brought life and took it away. It sheltered the spirits of the dead, who in turn helped it to flow for the living. But because of the way it operated, the population was divided on how they felt about it.

Those who completely surrendered to the Lifestream after their deaths began to lose their individuality. Eventually not only the knowledge they gained in life, but their very memories, began to intersperse through the Lifestream and mingle with everyone else's knowledge and memories. It was not unusual for someone to wonder where they had experienced a certain thing or how they knew a particular person. They could rarely remember, usually because those memories belonged to someone else. Those who had lost hope were among this group, as well as those who wanted above all to serve the planet.

But there were others who refused to surrender. They would not obstruct the Lifestream's flow; they would assist its movement and they wanted to help, yet they held onto their knowledge and their memories. They fully remained the people they had been in life. Zack Fair and Aerith Gainsborough were among this group.

Still others were disgusted by the whole concept of the Lifestream and would not willingly do anything to help it help the planet. They believed the entire system on Gaia was corrupt and needed to be either changed or obliterated in favor of something better. Sephiroth was among this group.

Zack had heard that Sephiroth had traveled through the Lifestream to a place between Heaven and Earth, a palace rumored to have once been inhabited by one of Gaia's deities who had wanted to get a better look at the land below. Sephiroth had claimed it for himself and "reigned" from there. For some time Zack had wanted to go, to try to talk to his dear friend and break through the insanity still clouding his mind. Once the geostigma crisis had begun, he had known that it was time. He had to get Seph to stop this craziness. And Aerith had agreed, but had warned him to be careful. Part of her had wanted to go with him, but she knew this was between Sephiroth and Zack alone. What was more, she had needed to stay to watch over Cloud, who was sinking further into depression.

Zack's heart had been divided. He wanted to be there for Cloud too. But he knew Aerith would take good care of their friend. And Cloud also had all of his still-living friends to rally around him. Seph did not have anyone. And if Zack could convince him to take this illness away, that would be a huge weight off of many shoulders, Cloud's included.

And so he had begun his journey. It was a surreal path that was his to take, following not only the Lifestream but the in-between world. The scenery was amazing, from barren deserts to lush waterfalls and sprawling meadows. Aerith would love it. Maybe when everything was over, he could bring her along the path for pleasure.

But not everything had been pleasant. Along the way he had also seen countless people afflicted by geostigma. He had witnessed the fevers, the pain and anguish, the memories that plagued their minds and caused the illness to flare up and advance to the next stage. It outraged and alarmed him. Seph had fallen too far. Even with his goals of wanting a better world, how could he think that all the sufferers of geostigma deserved what they were going through? Or did he even think that at all? What if he did not even care, but he just wanted to use them as pawns in his latest plan? The thought angered Zack. At the same time, it made him sick. That was not the Seph he knew. Not at all!

Seph had been such a kind man, so serious with a hidden sense of humor. They had experienced so much together--so many missions, so many long days at the base doing paperwork, so many long nights spent talking or watching TV or playing games. Seph had tried to teach Zack about chess, and Zack had tried to interest Seph in Twister. Neither attempt had gone very well. But those had been happy times. Zack had been proud to call Seph a friend.

But he had died at Nibelheim. In his place had come this nut determined to take back Gaia for its "rightful" ruler, Jenova--and later himself. It made Zack feel like crying if he dwelt on it too much.

After death Angeal's mind had been restored to him. Zack had been able to reunite with him again and he had been living with Zack and Aerith. But Seph was too troubled. He had not regained his sanity. If anything, death had made everything worse, especially when he had been faced with the Lifestream. On the one hand, he was pleased by all of the knowledge he had gained from it. But on the other hand he abhorred the Lifestream itself, seeing it as a cruel device thought up by the planet itself to take away everyone's freedom and eventually their sanity after a mortal demise. He had refused to remain within it after gathering his knowledge.

As soon as Zack saw the white-columned building in the distance, he knew it was Seph's place. It was spacious and magnificent enough to match the images he had in his mind, but what was more, he could sense Seph there. He had been feeling his friend's presence all along the way, growing stronger the further along he got. Did that mean that Seph sensed him, too? What kind of reception would he get? They had not spoken since Zack had tried to talk to him right before the final battle against Cloud and the others two years ago. And it had been one of the most heart-wrenching things he had ever done. All throughout their conversation, Seph had wavered between insanity and the friend Zack still loved.

A tall figure clad in black was waiting on the steps of the edifice. His silver hair blew about in the gentle breeze, the silver of his sword glistening in the light from above. It was drawn, gripped tightly in the left hand.

Zack swallowed hard. He would not draw his own sword unless he had no choice. He had to make sure Seph knew that he was not here on a mission of aggression.

"Seph!" he called as he drew closer.

The figure remained in place, as if frozen and inanimate. But the emotions moving through the green eyes very clearly said that this was still a human, not a statue. Somewhere beyond the talons of madness, Seph was still there. Seph could never die, even if he was buried deep within a stone heart. Zack wanted to run over, to hug the older man close and reassure him that he was still loved. But if the insane Seph was in control, he would probably consider it an insult for a "mere, wretched human" to touch him. And Zack did not want to start things off by making a sudden move.

So he stopped at the steps, looking up at the other. "Hey Seph," he said quietly. His heart twisted, threatening to leap into his throat. Just seeing that cold look would be enough to make most people give up. But this was Zack.

A sneer crossed features that had once been warm. "You're still using that pathetic nickname," Sephiroth commented. "I'm ashamed to even hear it spoken. Is that a fitting name for one who has gained the knowledge of the universe?" He kept his sword at his side, but did not raise it. "My name is Sephiroth."

"You're still Seph," Zack answered, keeping his voice steady. "Even if you don't want to remember that he exists, I do!" He took a step forward, lifting his foot to place it on the bottom stair.

Now the Masamune was brought to Zack's throat. "I could have prevented you from coming here," Sephiroth said. "I could have called down the wrath of nature and devastated you so thoroughly that you would never have dared to approach. But I let you come for a reason." He pressed the tip of the blade against Zack's throat just enough to cause discomfort. "I wanted to see if you came for any reason other than a futile effort to try to get through to 'Seph.'"

Zack kept his eyes on Seph, despite the sword pressing on his voicebox. "I came to talk to you about what's happening down there," he said. "You sent this geostigma thing, didn't you?"

"Mother sent it," Sephiroth replied.

"But you're controlling Jenova now, aren't you?" Zack said. "You're so powerful now that you broke free of her control. Or you think you have, anyway." Zack's look turned pleading. "She's still influencing you, Seph! Can't you see that? If you really want to break free, then you've gotta call off this geostigma. It's affecting kids the most! It's just awful!" He swallowed. "The adults have it really bad, too. Even Cloud . . ."

"Yes, I know. Cloud has geostigma." The cruel smirk returned. "Every time he thinks life will be better for him, it takes a turn for the worst. Isn't that how it always is? Both you and I have experienced it. Even you couldn't stay so ridiculously cheerful in the face of all the torture you endured. You finally had to accept that life and people are not how you always tried to claim."

"Accept nothing!" Zack retorted. "Most people really are good and kind and want to do what's right, even if they don't know what to do or if they get a little mixed up. And life is great! Just look at all the stuff down there, and even here! Trees and running water and mountains and animals and . . ."

He was interrupted by a chuckle, one that quickly evolved into an outright laugh. It was a heartless, unfeeling sound. "Are you sure you're not biased?" Sephiroth said. "What about the greed? The selfishness? And what about the wastelands? Geostigma? Even natural disasters? One flood can wash away all of the things you esteem so highly."

"I've seen both the good and the bad," Zack said. "I'd rather think about the good! A flood or a fire or whatever can't wash away the good in people. And Seph, even if you could make over the whole planet like you want to, you couldn't take away the bad. It'll always be there, just like the good!"

"I'll force the people to be good," Sephiroth said. "There won't be any of the corruption that you see on Gaia now. Everyone will live in unity."

Zack stared at him, aghast. "But . . . you can't just take away their free agency like that!" he protested.

"Take it?" The green eyes flamed. "They've abused it, time and again. Why should they deserve to make their own decisions after they've already proven they're incapable of it?"

Slowly Zack shook his head, still staring. "You'd just have a bunch of robot people!" he cried. "It would be like what you hate about the Lifestream so much, how it zaps people's individuality!"

"Over time they'd learn what would make them happy and what wouldn't," Sephiroth said. "Then they would begin to regain some of their freedoms." He pulled the Masamune away from Zack's throat. "I was hoping that a meeting with you would be interesting. Instead it's the same tired speeches I've always heard."

"Maybe because you need to!" Zack said. "Nothing ever sinks in!"

Sephiroth turned to walk up the rest of the steps. "I'm not going to waste time with your naive behavior," he said. "Before long I will be able to channel my spirit through one of my avatars. Then I will face Cloud in battle again."

Well, staying at the bottom of the stairs was not going to work. It was time for a sudden move. Zack ran forward, leaping up the steps two at a time. Before Seph could even turn around, Zack was grabbing his upper arm. The insane man stiffened.

"This is just what I mean!" Zack cried. "Seph never would've let this happen. He never would've dreamed of it."

"Your friend was weak."

The words were cutting deep, but there was no time to concentrate on them. "I guess he is, if he won't even keep trying to fight back," Zack shot back. "If Seph's still in there, he'd be struggling against this with everything he could muster! It was Seph I looked up to and wanted to be like. It was Seph who was honored as a hero."

The older man whirled, striking Zack across the face. "He was never a hero!" he said. "Neither am I. I'm something far greater."

Zack stumbled back, raising a hand to his sore cheek. "You're just plain crazy," he said.

And something inside him seemed to break. Here he was, standing staring at a stranger who had once been someone Zack had trusted with his very life. His cheek was still stinging from the attack, but not so much from the actual physical blow as it did what it signified.

"What happened to us, Seph?" he choked out.

The green eyes flickered. "I . . . don't know." Now Seph sounded weary and sad, not at all the raving madman he had been a moment before. Maybe what had broken inside Zack had affected him, too. "You . . . were a good friend to me, Zack. You stood by me when no one else did or would. And I betrayed you. I'm still betraying you."

Before Zack could react, the eyes hardened and the sneer returned. "Listen to that," Sephiroth taunted. "I don't know what came over me. It's like a parasite that suddenly takes control of my speech."

Zack straightened up, his eyes narrowing. His hope was back. He should have never let it waver.

"That's the real you!" he declared. "If anyone's a parasite, it's this crazy guy that invaded my best friend's mind and took over his body!"

Sephiroth raised a hand to his forehead. For a moment it lingered there, as if he was pained. But as he drew his hand away, his expression was more unforgiving than ever. Zack's heart was pierced again.

"You even dare to come here, expecting help from me after you betrayed me at Nibelheim?" Sephiroth said. "I would have let you come with me, even though you aren't descended from Mother. But you turned against our friendship."

Zack opened his mouth. His voice was not working. But at last he managed to choke out words. "I . . . I didn't want what you wanted then!" he cried. "I couldn't go with you, not when you'd burned down Nibelheim. You weren't the Seph I knew any more!"

"Weightless excuses. You betrayed me, just as everyone betrayed me!" Sephiroth lunged, drawing the Masamune as he swung it at Zack.

The brunet stumbled, dodging the blade. "Seph, no!" he pleaded. "I don't want to fight you!" His throat was dry and parched. Just when he had thought he was getting a little bit closer to his friend, it seemed like Seph had been buried even further. The Masamune was coming at him again. Zack jumped out of the way. He needed to draw his sword, and yet something was holding him back. Maybe if Seph saw that Zack would not defend himself, he would put the thing away.

Or maybe that was just foolish thinking. Sephiroth's eyes were crazed as he flew at Zack, the sword gripped tightly in his gloved hands. He slashed madly in every direction. It was all Zack could do to keep up with the motions and avoid them.

"Fight me!" Sephiroth demanded.

"No!" Zack retorted. "It wasn't supposed to be like this. I don't want to fight you, Seph. I never wanted to fight you!" He jumped onto a column that had broken and was laying on the white marble platform.

Sephiroth raised his hand. The column began to move forward. Zack yelped, strugging to stay on it by running in place.

"This wasn't one of my best ideas!" he moaned.

"Neither was coming here at all," Sephiroth replied. He drew his hand forward and held the palm straight out. The column came to an abrupt stop, sending Zack flying. With a grunt he crashed down on a wide landing between two sections of stairs. But he would not stay down for long. He pushed himself up, looking to Seph.

"Unfortunately, I can't stay here to continue this," Sephiroth said. "But I don't want you interfering." He moved so his hand was palm-up. As he began to slowly raise it, Zack stared in astonishment. The marble around him was suddenly shifting and shaping. Bars began to rise up around him on all sides. He was being trapped in a cage.

He gripped the cold bars, staring out at Seph. "What the heck?! Seph, what are you going to do?" He pushed his hand between the bars in desperation, reaching for his friend. "You can't keep me in here!"

"I'll let you out when I get back," Sephiroth answered. "Then we can continue this." He smirked. "You'll be able to watch it all, of course." With that he spread his black wing. A mighty flap took him into the sky. Zack could only stare after him helplessly as the loose feathers floated back to the ground.

"Seph," he whispered. His shoulders slumped. He had failed to do anything to stop the madman. And now . . . now Seph was going to fight Cloud again. Would Cloud even be ready for it? He had been in such a quandary the last couple of months. From what Zack had been able to see on his journey here, however, Cloud was getting some of his confidence back. He had even determined to try to forgive himself for the deaths he still blamed himself for not preventing. But to face Seph right now . . . would that be too much? Maybe that would open the scabbing wounds all over again.

No, Zack had to believe in Cloud. And . . . he had to keep believing in Seph, too. No matter how hard it was.

He turned his attention to watching the events in the world below. Seph was not holding back. He was dueling Cloud aggressively, sending him flying inside the Shinra building through a hole in the wall. They battled for a short time before Cloud stepped out onto a ledge. Sephiroth followed. Zack's mouth dropped open in disbelief. Seph was _throwing parts of the building_ at Cloud! Cloud dodged and sliced his way through, but Seph always found more. What the heck was he trying to do? This was not a fair fight at all!

Just like in the final battle before Meteor, Zack was powerless. All he could do was sit and stare as two of his best friends dueled. Seph was making fire start up all around Cloud. Now he was breaking another huge chunk of building free with telekinesis. He sliced into it himself, vanishing into the onslaught. Cloud struggled to leap through the debris, using his sword whenever possible. Then Seph was flying at him again.

This was horrible! Zack could not stand to keep watching, but he could not look away, either. He wanted to cry or scream. He wanted to turn back time so that Nibelheim never happened.

He wanted his friend back.

His eyes widened in horror. Seph had overpowered Cloud and was impaling him through the shoulder. He wanted to know what Cloud cherished most, he said. He wanted the pleasure of taking it away.

What would Cloud do? He was sprawled there, gripping the blade in one hand. . . . His blue eyes flamed. He shoved the sword out of his flesh as he got to his feet. He was not broken. He was focused. And he was ready to defeat Sephiroth. There was nothing he didn't cherish, he informed Sephiroth.

Zack averted his eyes. He was ecstatic that Cloud was determined to fight for his loved ones. But he did not want to see Seph be killed again. Not that he would really die, when he was just channeling his spirit. But then the avatar would die, wouldn't he? Oh wow, this was such a big mess. . . .

And a lightbulb went on in Zack's mind. Whether it had been intentional or not, Seph had forced Cloud to do his very best by pulling all these awful tricks. Cloud had found his full strength in this battle because he had needed to completely focus in order to remain alive.

Zack rested his forehead against the bars. Seph did not do things without a reason. But did that mean he had _wanted_ to push Cloud to his limit?

He looked up as a bright light appeared. As it faded, Seph was half-kneeling on the marble, his wing wrapped around himself. His sword was in his left hand, of course, and he was clutching at his chest. A pained expression crossed his features.

Zack gave him a worried look. "Seph?" he called.

The other man stiffened, his head snapping up. Apparently he had forgotten that he had an audience--or at least, he had not realized that he had landed back at the exact spot where Zack was caged.

Zack reached through the bars again. "Seph, are you okay?!" he exclaimed.

"I'm fine." Seph straightened, spreading his wing away from his body.

Zack peered at him. No clues to the truth were visible on his face. "Seph . . . you were trying to help Cloud, weren't you?" he said, lowering his voice.

"_Help_ him?" Sephiroth said in derision. "He isn't worthy to be my opponent unless he gives his all in combat. And until last night, he was too afraid to fight at all."

"You were pushing him to do his best," Zack said. "You knew he needed that!"

"And I thought I was supposed to be the crazy one."

Both of them stiffened as a gunshot rang out. As they stared at the scene below, Cloud was struggling to stand after being shot by Yazoo. Now he was charging at Yazoo and Loz. They retaliated. An explosion ripped across the rooftop.

_"Cloud!"_ Zack screamed.

Sephiroth turned away from the scene. "Well," he said, "it looks like Cloud is departing that life anyway."

"It's not his time," Zack retorted. "He's not gonna die." He gripped the bars. Cloud would have to be badly hurt in any case. He was wounded from the fight with Seph, too. Zack's heart was twisting in panic and worry.

"Seph, let me out of here!" Zack pleaded. "Come on, I've gotta get to him!"

Sephiroth crossed his arms. "I'm sure the Ancient will be with him," he replied. "He won't be alone."

_Like you are?_ Zack could not help thinking. Did Seph _want_ him to stay? Again his heart was being divided. If only he could be in two places at once! If Seph wanted him here, then he wanted all the more to remain. Maybe it meant that the real Seph was breaking through. But Cloud . . .

Sephiroth held out his hand, palm-down. As he lowered it, the marble cage diminished.

"Go to him, then." Again he sounded weary.

Zack was dumbfounded. He stared at Seph, frozen to the spot.

"Go!" Seph gestured with his sword. "Before I change my mind."

Zack swallowed. He walked down the steps, hesitating for only a moment. There was still something he wanted to do here. And it was the right time. He launched himself at the stunned man, hugging him close. "Seph . . . I still love ya," he said. "Sephiroth Fair . . . that's supposed to be your full name." He pulled back with a grin. "You're my brother."

"Bah." Sephiroth turned away. "You're a fool."

"Maybe," Zack agreed, "but being friends with you . . . that's one of the smartest things I ever did." He nodded firmly, crossing his arms. "I'll be coming back. You're still in there, Seph. And I'm not gonna give up until you're completely in control again!"

"That's never going to happen." Without warning Sephiroth opened a portal under Zack's feet. The brunet yelped in surprise as he fell through. What was Seph doing now? Where was he going to end up? Had he been wrong about Seph's intentions? Or was Seph mad because Zack wanted to leave to go to Cloud?

He landed in a space of white, sitting down hard. For a moment he just sat there, dazed.

"Well, that was quite an entrance!"

He started, looking up at Aerith. She was standing over him, her hands on her hips as she waited for an explanation.

He grinned, leaping to his feet. "Thanks to Seph!" he said, sticking his thumbs through his suspenders. "He's really there, Aerith. I know I can save him! I just know it!"

She blinked in surprise. But then she smiled, genuine happiness for Zack in her eyes. "That's wonderful," she said. "But right now we have a visitor." She nodded to Cloud's wounded and unconscious body. He had arrived just a split second before Zack had landed here.

Zack's eyes widened. "Okay!" he exclaimed, hurrying over to his other best friend. "Let's see what we can do to help you, buddy."

He watched as Aerith came over as well, using her healing powers to tend to Cloud's injuries. Relief washed over him as the wounds began to glow and mend. Cloud was going to be okay.

And in time, Seph would be, too.

That was a promise.


End file.
